A general photoelectric conversion element using a semiconductor can not sufficiently absorb a solar spectrum as a result of an absorption wavelength band to be determined by a band gap of the semiconductor. A Si single-crystal solar cell, for example, can only absorb light of 300 to 1100 nm to provide power generation efficiency of about 20% or less. Accordingly, in order to enhance the power generation efficiency of a general photoelectric conversion element, it is necessary to introduce an absorption region into a photoelectric conversion layer to absorb long-wavelength light which the photoelectric conversion layer can not absorb intrinsically.
In addition, a method to increase carrier excitation has been proposed in order to provide an efficient photoelectric conversion element. The method generates enhanced electric fields due to plasmon resonance in a metal nanostructure.